In current multi-hop OFDMA based wireless communication systems, such as IEEE 802.16j, the TDD frame structure shown in FIG. 1 comprises two subframes, one for downlink and the other for uplink. FIG. 1 demonstrates the single radio non-transparent frame structures with minimum configuration for both the MR-BS (multi-hop relay base station) and RS (relay station) where the downlink and uplink subframes are further partitioned into access and relay zones. The access zone will be used for an MS communicating with either the BS or the RS, whereas the relay zone will be used only for BS to RS or RS to BS communications.
It may be required that all BSs (MR-BSs) within a deployment are upgraded to operate on new standardised protocols such as that defined in IEEE 802.16m. The upgraded deployment may also consist of new RSs also operating on the protocols defined in 802.16m. In this deployment scenario, it is crucial that full legacy support is enabled. Here, “legacy” refers to the pre-existing deployment of 802.16e MSs and 802.16j RSs. Considering a mixed deployment scenario comprising:                Legacy 16e MSs;        Legacy 16j RSs;        New 16m BS (MR-BS);        New 16m RS;the new 16m BS must be capable of providing full protocol support to each entity.        
FIG. 2 demonstrates this scenario where a 16m BS is serving both 16j and 16m RSs that are located within the same cell.
From the 16m BS point of view, the frame structure must be capable of supporting such a configuration without compromising legacy support. A general overall frame structure is shown in FIG. 3, where the 16m BS downlink and uplink subframes have been partitioned into legacy and 16m (new) zones. These zones are then further dissected into access and relay zones.
FIG. 3 also shows the frame structures for the 16j and 16m RSs where idle periods are required to avoid intra- and inter-cell interference. The R-TTG represents the relay transmit-to-receive transition time gap and the R-RTG is referred to as the relay receive-to-transmit transition time gap. The R-TTG allows time for the RS to switch from transmit (Tx) to receive (Rx) mode and, during this gap, the RS is not transmitting modulated data but simply allowing the RS transmitter carrier to ramp down, the Tx/Rx antenna switch to actuate, and the RS receiver section to activate. The R-RTG allows time for the RS to switch from receive (Rx) to transmit (Tx) mode and, during this gap, the RS is not receiving data but allowing the RS transmitter carrier to ramp up, the Rx/Tx antenna switch to actuate and the RS transmitter section to activate.